/Engine/Plugins/Runtime/NetworkPrediction/Source/NetworkPrediction/Public/NetworkPredictionProxy.h
The init function binds to the templated methods on UNetworkPredictionMAnager. This will "bring in" all the templated systems on NP, so this file should only be included in your .cpp file that is calling Init.
template<typename ModelDef> void Init ( const [FInitParams](API\Plugins\NetworkPrediction\FNetworkPredictionProxy\FInitParams)< ModelDef > & Params )